Workers in the art of making and using magnetic recording apparatus are well aware that the media therefor experiences tremendous wear problems. A magnetic recording tape slides across a magnetic recording head, guide members, etc., at relatively high speeds and is apt to undesirably abrade both itself and the head, with a foreshortened useful life for both.
A related problem is that of undesirably high friction between the tape surface and the head surface. To ameliorate abrasion, workers typically require that a tape coating exhibit a certain (maximum) coefficient of friction--this also reduces the reel-force necessary to pull the tape past the head. To reduce friction and enhance wear, workers have resorted to various expedients such as "lubricated" tape coatings.
Such lubricated coatings are particularly important for magnetic tape (or like flexible disks) of the type used in computer recording, or in conjunction with video or audio recording where the relative head-medium velocity is very high, producing aggravated abrasion and reduced life (durability) of both head and media. Thus, workers have resorted to various lubricant means for such tape coatings and like media (e.g., see the following U.S. Pat. Nos. 3,490,946, 3,492,235, 3,523,086, 4,431,702, 3,983,302, 3,837,912, and 3,597,273).
It is an object of this invention to address such problems and particularly to teach novel magnetic recording compositions including improved lubricant systems, especially for such media which use chromium dioxide magnetic powder.
It is a more particular object to do so using a fluorosilicone (FS) lubricant compound in combination with a "fatty acid ester" lubricant (FAE). More particularly, it has been found that such an "FS/FAE" lubricant provision of a novel "high density/high performance (e.g., 30,000 flux transitions per inch feasible) chromium dioxide computer tape" that uses, a magnetic coating with FS/FAE lubricants to good advantage. For instance, compared with a standard ferric oxide computer tape, such a novel tape coating can give much higher storage density yet remain less abrasive than many standard ferric oxide tapes and give more durability than most--something that will surprise workers!
A salient form of the new magnetic recording compositions is for magnetic CrO.sub.2 coatings for high density-high performance computer tape. Such tapes have heretofore exhibited unsatisfactory durability and abrasivity, etc.--such as to be commercially unattractive. For instance, their durability and abrasivity are unsatisfactory--problems which an FS/FAE lube system of the invention addresses.
The "fluorosilicone/FAE-lube" coatings of the invention are characterized by a fluorosilicone oil component in combination with a compatible stearate or like fatty acid ester component.
Now workers have, of course, incorporated lubricant components into a magnetic recording layer (with the pigment, binder, etc.). For instance, lubricants such as molybdenum disulfide, graphite or a wax have been suggested for use with a magnetic powder like gamma Fe.sub.2 O.sub.3 and a binder like polyvinyl chloride. But such lubricants are not effective in giving the kind of superior durability (and low abrasivity) we desire; also, in heavy concentrations they can impair magnetic performance (e.g., see U.S. Pat. No. 4,431,703).
And workers are familiar with suggestions for using such lubricating agents as parafinnic hydrocarbons, fatty acids or esters or silicone oils (e.g., dimethyl- or diphenyl-silicone oil)--yet those don't give adequate durability or lubricity to the media, and can cause "bleeding" or "blooming" when used in large concentrations.
Some workers have suggested certain organo-polysiloxane/-polysilicone compounds as lubricants for magnetic recording media (e.g., see U.S. Pat. No. 3,993,846, or U.S. Pat. No. 4,007,314, or U.S. Pat. No. 4,131,717--or U.S. Pat. No. 4,007,313 mentioning an organo-silicone-fluoride lubricant; U.S. Pat. No. 4,431,703 suggests a like lubricant with various magnetic materials such as CrO.sub.2).